If you cannot connect your printer to the printing software computer, please follow the next steps.

1. Make sure the USB cable is properly connected to the computer
2. Make sure the printer is turned on.
3. Check the connection settings of the software and be sure the right COM port is selected. Mosts programs have a COM port autodetect, which mostly works. But if you have for instance bluetooth devices installed on your computer the autodetect is most likely to select the wrong COM-port. Also check if the connection speed in the connection settings of the print software is set to 115200. This connection speed should also be the same in your printer, check this on your printer by going to settings -> connection
4. Is there is no COM-port displayed in the printer settings, which corresponds to your printer. There is no driver installed yet on your computer.
5. Reinstall the software (Repetier-Host for FELIXprinters) and make sure you have administrator rights. This program contains printer drivers for the Tec and Pro series.
6. If this doesn't work, please follow instructions below to manually install the 3d printer drivers.

Install Printer drivers

TEC 4 / 3.1 and older

These board have an arduino MEGA 2560 based control board. They need FTDI Virtual Com port drivers.

• Install Repetier-Host for Felixprinters and the drivers are installed automatically.
• Or manually download it from here. http://www.ftdichip.com/Drivers/VCP.htm
• Special case in windows 10, sometimes the only way for the FTDI driver to install correctly is to update it in device manager. In some cases windows will automatically install the incorrect driver by windows update (named something like USB Converter) and assign a new COM port.

Pro series

The regular Pro series have an arduino Due based control board.

• Mac driver installation not necessary
• Windows, please install repetier-host 

Pro touch

For the FELIX pro touch the following drivers are required to connect via USB.

Pro Touch - USB drivers windows and Mac OS X

For at least Windows 10, the FTDI driver needs to be updated in device manager.  Windows will download the new driver (named something like USB Converter) and assign a new COM port. What’s odd, is none of my other Arduino dev boards are having this problem – all using FTDI just fine.